Nicole Cox

One of WA’s foremost marine experts has described the remarkable exchange between a humpback whale and great white shark that shut Perth’s northern beaches on Thursday as “nature being played out on our doorstep”.

The comments came as the City of Stirling reopened beaches between Floreat and Watermans, hours after authorities tracked the four-metre shark pursuing a six-metre whale.

Surf Lifesaving WA said the shark was first sighted at Swanbourne on Thursday morning. The whale was last seen around Hillarys around 2pm, but there was no confirmation of a shark nearby.

City Beach and Floreat beaches were the first to be closed after reports that the whale and shark were between 25-100 metres offshore.

Council beach rangers progressively closed beaches as the animals moved further north along the coast.

Department of Parks and Wildlife senior marine wildlife officer Doug Coughran said photographs of the whale indicated it was in poor health and was most likely swimming close to shore to protect itself.

Advertisement

“In this case...it’s come into shallower water and traverse up and down the coast where it can’t be ambushed from below, from the deep,” Mr Coughran said.

“From what I’ve observed over the years, any animal that’s compromised will do things to increase its survivorship and avoid being picked off.

“They are afforded some protection from travelling closer to shore. It’s a learnt strategy that they will try and be invisible.

“Basically what we saw today was nature being played out on our doorstep.”

Mr Coughran, who has monitored humpbacks for 30 years, estimated that about 30,000 of the whales travelled up and down the WA coast during the migration period.

“It’s part of the natural process with the recovering population of humpbacks. We’ve got a really good recovery rate since the late 1960s,” he said.

A Fisheries Department spokesman warned that if the whale was injured or in distress it could potentially attract more sharks to the area.

Surf Lifesaving WA expressed concern on Twitter that surfers had refused to leave the water as beaches between City Beach and Waterman were closed by the City of Stirling.

It is understood the warning related to surfers at Trigg Point.

The sighting comes a day after baited drum lines set one kilometre off the coast were removed after WA's controversial shark catch-and-kill policy ended.

Although final figures for the number of sharks and other animals caught have not yet been released, Premier Colin Barnett has hailed the success of the program, which was aimed at great white sharks, tiger sharks and bull sharks.

The majority of those caught were tiger sharks, but a blacktip and dusky whaler were also caught and released alive. No great white sharks were caught.

Data from the Department of Fisheries for the period from January 25 to March 16 shows 31 sharks were killed while a further 14 were found dead on hooks, including two mako sharks.

Earlier this month, the government applied to the commonwealth to continue the program for three more years.

That would see up to 72 baited drum lines set one kilometre off the metropolitan and southwest coast between November 15 and April 30, starting this year, and would be reviewed in 2017.